The present invention relates to a suspension system for supporting a single steerable front wheel of a vehicle such as a customized motorcycle, typically known as a “chopper.”
A chopper usually has one or two pairs of elongate members that extend in a substantially parallel manner forwardly and downwardly from the vicinity of the vehicle's handlebar at a rake angle of about 45 degrees to about 60 degrees from the vertical to give the chopper its unique and interesting look. One pair of the elongate members may mount opposite ends of the vehicle's front wheel axle, or may pivotally connect with ends of arms that have overlying opposed ends that mount the vehicle's front wheel axle. If a second pair of elongate members is present, the members of the second pair usually connect with the elongate arms that support the front wheel axle and serve to transmit vibration from the front wheel rearwardly and upwardly toward the handlebar where suspension system springs are provided to cushion the vibration.
The arrangements just described are disadvantageous because they do not deal with front wheel vibration in the vicinity of the front wheel where it originates, but rather transmit front wheel vibration rearwardly and upwardly through a pair of the elongate components to be dealt with by springs which must be heavier than would be needed if the vibration that originated with the front wheel had not been introduced to and transmitted rearwardly and upwardly along the elongate members.
Disadvantages also arise because the arrangements just described bring a large amount of “trail” and attendant steering difficulty to choppers. “Trail” is the distance measured horizontally along the ground level between a point that lies directly beneath the front axle, and at a point defined by the intersection of the ground level with an imaginary line extended through, and at the same angle as, the vehicle's steering stem. While a small amount of trail measurement is desirable to give the vehicle good handling characteristics, the trail measurement is best minimized. However, most chopper suspension systems have a design that leaves the trail measurement relatively large, even though considerations of trail measurement are far more important than are rake angle considerations in determining how well any given frame and fork geometry combination will handle on the road.
Suspension systems embodying features of the present invention are advantageous in that the suspension system deals with front wheel vibration in close proximity to the front wheel instead of transmitting this vibration upwardly and rearwardly along relatively heavy elongate members, and in that the suspension system tends to provide the steerable front wheel of a chopper with a relatively small or minimal trail measurement and desirable accompanying over-the-road stability.
Suspension systems embodying preferred features of the present invention also are advantageous in that they provide for essentially vertical (up and down) movement of the front wheel in response to the front wheel dropping into a chuckhole or engaging a pronounced bump in the road—and, in that this vertical up-down front wheel movement is immediately cushioned at locations quite near to (indeed at locations on opposite sides of) the front wheel, rather that requiring that the up-down movement of the front wheel be transmitted as a jolt to near the handlebar where the force of the jolt is finally cushioned by remotely acting suspension system springs.